During Phase I, the feasibility of a simultaneous ABR-TEOAE acquisition system was studied and demonstrated. Data from 12 adults were collected and processed off-line. Three experiments were conducted. In experiment l, the feasibility of simultaneous ABR and TEOAE acquisition using linear, non-linear, alternating and non-alternating stimuli was demonstrated. In experiment 2, an alternative stimulus artifact reduction method, Scaled Template Subtraction (STS), was implemented and tested successfully. The experiment showed that linear stimulation combined with the STS method has at least three advantages over the current Derived Non-Linear Method used to acquire TEOAEs: it a) provides more accurate pseudo-thresholds, b) reduces artifact contamination, and c) provides for more efficient data acquisition. Experiment 3 tested a cross-modality noise cancellation technique and demonstrated that both OAE and ABR signal- to-noise ratios can be improved by using noise levels from EEG and acoustic inputs simultaneously. During Phase II, these techniques will be implemented in real-time and expanded to include pure tone stimulation. A new probe with a broader frequency and intensity range and stimulus artifact canceling preamplifier will also be developed. Clinical trials will be conducted in Year 2 to test the system under a range of operating conditions, including intraoperative monitoring and infant hearing screening. PROPOSED COMMERCIAL APPLICATION: The proposed TEOAE /ABR system will enable clinicians to evaluate hearing status using both TEOAEs and ABRs simultaneously. Advanced stimulus artifact cancellation methods will improve pseudo-threshold determination and testing efficiency and reduce stimulus artifact contamination. The proposed device will find immediate commercial application in all areas of hearing testing.